As for minus ion generating methods, a minus ion generating method has been designed, in which an artificial fall is installed in a space, thereby mist is generated mechanically, taking notice of “Lenard effect” by which a large number of minus ions exist in the vicinity of a fall. Further, the other minus ion generating method has been designed, in which wind transported by a blower is used and a centrifugal force is used, thereby fine mist is produced, resulting in that minus ions are generated. Furthermore, a corona discharge method has been designed, thereby minus ions are electrically generated.
According to the above-mentioned method in which an artificial fall is installed in the room, thereby fine mist is generated, resulting in that minus ions are generated in the air, a particle of water drop broken in the vicinity of the fall is too large to become a small particle of water drop, resulting in that generation of the minus ion is restricted. Also, a particle of water to be fined is still large in the vicinity of the fall, therefore it can be recognized that plus ions are generated. According to the method, a large amount of water must be circulated and flown simultaneously, and vast cost of equipment is required concerning cost.
According to the above-mentioned method in which the centrifugal force of wind transported by the blower or the like is used, thereby fine mist is produced, resulting in that minus ions are generated, likewise, a particle of water is not be sufficiently fined, resulting in that a large number of plus ions are generated, and a number of minus ions are not sufficiently generated. Simultaneously, therein, much drain is generated.
In any of the above-mentioned methods, the particle of water to be generated is still large, resulting in that there exist a large number of plus ions and there are a small number of minus ions to be generated.
According to the above-mentioned method using the corona discharge phenomenon in which minus ions are electrically generated, not only the minus ions but also plus ions are simultaneously generated, and further a period between appearance and disappearance of minus ions is short, resulting in that there occurs a practical problem. Additionally, ozone and nitro-oxide are generated. There is a fear that a harmful gas might occur owing to dirty of electrodes. Also, it is difficult to always stabilize discharging state, so that the minus ions cannot be stably and safely generated.
In any of the above-mentioned methods, minus ions are being produced, while plus ions are being generated. Therefore, an effect of minus ions has been reduced.